Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and a rotor including one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid. Such configurations may also include power converters that convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency.
Traditionally, wind turbines include a control module, which attempts to maximize power output of the turbine in the face of varying wind and grid conditions, while satisfying constraints like sub-system ratings and component loads. Based on a determined maximum power output, the control module controls operation of various turbine components, such as the generator/power converter, the pitch system, the brakes, and the yaw mechanism to reach the maximum power efficiency.
The performance of a wind turbine, in terms of annual energy production (AEP), can be improved through control changes and/or various products, features, and/or upgrades available for wind turbines. One or more benefits of a control change and/or an upgrade is typically determined using a toggle method. For example, for upgrade benefit verification, the turbine is operated at a baseline operational state (i.e. without the upgrade) and the operated at an upgraded operational state (i.e. with the upgrade). For control parameter changes, the control parameters are toggled through a repeating sequence of control parameter states. Each state represents a set of control system parameters or settings, which affect turbine operation. During the toggle test, wind speed and power production measurements are recorded. The wind speed and power data collected during each state is used to assess the turbine performance during that state. Typically, the wind speed is measured using the turbine nacelle anemometer, which is generally mounted on the nacelle behind the rotor but may be located at any suitable uptower location. Performance values for each state may then be computed and compared. As such, the comparison can be used to validate a performance gain or to select a state which provides a higher performance.
The nacelle anemometer approach, however, is sometimes hindered due to imprecision of nacelle anemometer measurements and the projection of these measurements into AEP estimates. In addition, the nacelle anemometer does not directly measure the desired free stream wind speed at the turbine because of the aerodynamic effects of the turbine. The relationship between the wind speed at the nacelle anemometer and the free stream wind speed, during turbine operation, is referred to as the nacelle transfer function (“NTF”). The NTF is determined and stored by the turbine controller and is used internally by the wind turbine to correct the wind speed measured by the nacelle anemometer to calculate the free stream wind speed.
However, toggle tests that use the nacelle anemometer to measure wind speed may also change the NTF. An NTF change creates a wind speed measurement bias that is different for the different operational states or modes. With conventional toggle tests and analysis, such bias in turn biases the determined or measured turbine performance in an unknown or unpredictable way.
As such, the present disclosure is directed to an improved system and method for validating a benefit of an upgrade provided to a wind turbine that addresses the aforementioned issues. More specifically, the present disclosure is directed to offset toggle methods for wind turbine operation that accurately and efficiently validate various upgrades provided to the wind turbine.